1. Field
The disclosure relates to a rubber composition in particular for a tire tread and more particularly for a tire intended to equip vehicles carrying heavy loads and running at sustained speed, such as, for example, lorries, tractors, trailers or buses, aircraft, and the like.
2. Description of Related Art
Some current tires, referred to as “road” tires, are intended to run at high speed and over increasingly long journeys, as a result of the improvement in the road network and of the growth of the motorway network throughout the world. In point of fact, since savings in fuel and the need to protect the environment have become a priority, it is important for the tires to have a low energy consumption. One of the sources of energy dissipation is the heating of the tire.
In the same way, it is known that the treads of the tires used in civil engineering are particularly sensitive to the increase in temperature. In point of fact, there is a constant search to improve the properties of tires and in particular their wear resistance and, conventionally, the improvement in the wear resistance is known to be reflected by an increase in energy consumption.
In order to obtain such an improvement in terms of wear resistance and energy consumption, attempts have been made to use finer reinforcing fillers in the tread, in particular “fine” carbon blacks, that is to say having a CTAB specific surface of greater than or equal to 90 m2/g, indeed even “very fine” blacks, that is to say carbon blacks having a CTAB specific surface of greater than or equal to 130 m2/g. However, in order to obtain the optimum reinforcement and hysteresis properties conferred by a filler in a tire tread and thus a high wear resistance and a low rolling resistance, it is known that it is generally advisable for this filler to be present in the elastomeric matrix in a final form which is both as finely divided as possible and as homogeneously distributed as possible. Such conditions can only be achieved insofar as this filler exhibits a very good ability, on the one hand, to be incorporated in the matrix during the mixing with the elastomer and to deagglomerate and, on the other hand, to disperse homogeneously in this matrix.
In point of fact, very fine blacks are known to be extremely difficult to correctly disperse in the elastomeric matrix and bring about a deterioration in the processability (in comparison with the use of the same content of coarser blacks). One solution for a person skilled in the art would be to use plasticizing oil or resin to improve the processability; however, it is known that the use of such plasticizers with these very fine blacks has the consequence of a very significant deterioration in the breaking energy properties (elongation at break and breaking stress properties).